Start-up method for an internal combustion engine

ABSTRACT

An internal combustion engine and a method of operating said engine, the engine having a plurality of cylinders ( 3,4,5 ) each respectively supporting a piston ( 6 ) therein, a fuel injection system ( 2 ) including a plurality of selectively operable delivery injector nozzles ( 10 ), and a gas supply system ( 7 ) for supplying gas to the delivery injector nozzles ( 10 ), each delivery injector nozzle ( 10 ) arranged to respectively deliver fuel by way of said gas directly into a said engine cylinder ( 3,4,5 ), the method including opening the delivery injector nozzles ( 10 ) of a first said cylinder and a second said cylinder such that gas within the first said cylinder is transferred through the delivery injector nozzle ( 10 ) thereof and into the gas supply system ( 7 ) resulting in gas being supplied to the delivery injector nozzle ( 10 ) of the second said cylinder to thereby effect the delivery of fuel by way of the gas to the second said cylinder.

This invention relates to fuel injected internal combustion engineswhere delivery or air injectors respectively deliver metered quantitiesof fuel directly into the or each cylinder of the engine by means ofcompressed gas. In engines comprising such two fluid injection systems,the metered quantities of fuel are delivered into the or each combustionchamber of the engine entrained in the gas, typically air, which issupplied from a pressurized gas source, typically a gas duct or rail.

In most engines, a delay is normally experienced between the initialrotation of the engine and the subsequent firing of the engine. Due tocommercial and user considerations, this delay or start-up period istypically desired to be as short as possible under a wide range ofconditions. For example, an engine may be employed for operation underambient and extreme ambient conditions. Efficient engine operation isimportant no matter the conditions.

In engines having a fuel injection system of the type above described,an important part of achieving a rapid start-up period is the readyavailability of compressed gas at an adequate pressure to assureeffective fuel delivery as close to start of cranking as possible.However, for cost and other considerations, it is not convenient toprovide a relatively large compressed air storage capacity or generationmeans and, in any event, there is also the risk of loss of pressure dueto leakage, particularly when the engine has been inoperative for aperiod.

Typically, a compressor driven by the engine is provided as the meansfor supplying compressed gas to a two-fluid fuel injection system asabove described. For both reasons of economy and energy efficiency, itis customary to select the compressor capacity to closely match the airconsumption rate of the engine during running conditions. Thus, thecompressor would typically require a certain period of time to increasethe air pressure to a suitable level as required during start-up. Thatis, the compressor, and thus the engine, must complete a number ofcycles before air is available for satisfactory injection of fuel at therequired pressure.

The above factors contribute to the lengthening of the period betweencommencement of the start-up sequence of the engine and the availabilityof air at the required pressure for injection of fuel. In this regard,the Applicant has developed several methods for minimizing the start-upperiod in certain engines.

In the Applicant's U.S. Pat. No. 4,936,279, there is described a methodof operating an engine during an engine start-up period. The engineincludes a gas supply system for supplying gas to the delivery or airinjectors. The gas supply system normally includes a gas supply volume,commonly known as an “air rail”, from which pressurized gas is suppliedto each of the delivery injectors. Compressed gas for the air rail isnormally supplied by a compressor driven by the engine. As alluded tohereinbefore, the compressor must however complete a number of cyclesafter engine start-up before the compressor can provide sufficientcompressed gas to pressurize the air rail to within a working pressurerange. The gas within the air rail and as supplied to the deliveryinjectors needs to be at a high enough pressure to enable the deliveryinjectors to inject a metered quantity of fuel into cylinders supportinga piston typically undergoing a compression stroke and thereforecontaining gas under a relatively high pressure. The pressure of the gasmust also be sufficient to enable satisfactory atomisation andentrainment of the fuel being injected. The method described in thispatent involves effecting one or more “pump-up” events by deliveringpressurized gas from respective cylinders of the engine into the gassupply system during the engine start-up period by opening the deliveryinjector nozzle for each cylinder undergoing a compression stroke of thepiston located therein. This results in a progressive increase in thepressure within the gas supply system until the pressure is within therequired working pressure range at which time the delivery injectors canbegin delivering fuel.

It is further known from the Applicant's subsequent PCT PatentApplication No. PCT/AU97/00438 filed on Jul. 10, 1997 that the deliveryinjector nozzle 10 may be opened and closed at successively closertimings to the top dead centre (TDC) position of a piston reciprocatingin a cylinder of the engine over a sequence of pump-up events to shortenthe start-up period of the engine. This patent application alsodiscusses holding the delivery injector nozzle open for a certain periodafter the engine has commenced firing to continue pressurising the gassupply system prior to the main source of compressed gas being able toadequately pressurize the gas supply system.

It has however been found that the period required to pressurize the airrail to within the working pressure range during start-up of the enginecan still be too long for certain engine applications. For example, incord or pull start engines as typically used in snowmobiles, smalloutboard engines and lawn-mowers, the start-up period needs to berelatively short, such that start-up can be achieved within the periodprior to full extension of the cord. Because the above methods require asufficient period of time for the engine to determine its angularposition and to subsequently pressurize the air rail by suitable means,these methods may therefore not be applicable for certain cord or pullstart engines. More generally, the ever increasing requirement forshorter start-up periods may result in these methods not being able toprovide for start-up periods below a certain point.

It is therefore an object of the present invention to provide a methodof fuel delivery for a two-fluid fuel injection system wherein the gasprovided to enable delivery of a metered quantity of fuel into acylinder of the engine is derived directly from a different cylinder ofthe engine.

It is a further preferred object of the present invention to provide amethod for enabling the reduction of the duration of the start-up periodfor an engine incorporating a two-fluid fuel injection system.

With this in mind, the present invention provides in one aspect a methodof operating an internal combustion engine, the engine having aplurality of cylinders each respectively supporting a piston therein, afuel injection system including a plurality of selectively operabledelivery injector nozzles, and a gas supply system for supplying gas tothe delivery injector nozzles, each delivery injector nozzle arranged torespectively deliver fuel by way of said gas directly into a said enginecylinder, the method including opening the delivery injector nozzles ofa first said cylinder and a second said cylinder such that gas withinthe first said cylinder is transferred through the delivery injectornozzle thereof and into the gas supply system resulting in gas beingsupplied to the delivery injector nozzle of the second said cylinder tothereby effect the delivery of fuel by way of the gas to the second saidcylinder, wherein each second said cylinder into which fuel is deliveredis operated to effect combustion of said delivered fuel for eachcylinder cycle.

The method according to the present invention may be used duringstart-up of the engine to facilitate the reduction of the start-up timefor the engine. It is however also possible for this method to be usedwhen the engine is operating under alternative conditions. For example,the method could be used to operate the engine under a “limp-home” modeif an air compressor supplying compressed gas to the fuel injectionsystem fails resulting in a loss of pressure within an air rail of thefuel injection system.

The method may be implemented so as to not effect the normal start-upfiring sequence of the cylinders, and each delivery injector nozzle andassociated cylinder may be operated to effect combustion of a saiddelivered fuel in the normal manner. That is, the method may beimplemented such that each cylinder remains operational to effectcombustion in the normal manner. Hence, there is no requirement to ceasefuelling to any engine cylinders (ie: to shut them down) or to ship thefuelling event on any cylinder whilst the method of the presentinvention is being used.

Preferably, the timing of opening and the open period of the deliveryinjector nozzle of the first said cylinder may be selected so as toprovide for a maximum possible pressure to be captured or transferredinto the gas supply system from the first said cylinder. This gaspressure may then be used to effect delivery of fuel by way of the gasto the second said cylinder. Typically, some of this gas pressure mayremain in the gas supply system after the fuel has been delivered to thesecond said cylinder such that he pressure in the gas supply system mayeventually be increased to a pre-determined level. As cylinder pressureis directly related to crank angle, the opening and closing events forthe delivery injector nozzle of the first said cylinder may preferablybe controlled with respect to crank angle. Typical timings for anyengine configuration for the opening and closing events for the deliveryinjector nozzle of the first said cylinder are between 90° BTDC and 10°ATDC. Preferably, the timing of opening of the delivery injector nozzleof the second said cylinder is selected so as to provide for a maximumpossible differential pressure between the pressure within the gassupply system and the pressure within the second said cylinder. Thisensures that the fuel may be satisfactorily delivered into the secondsaid cylinder by way of gas.

Preferably, the delivery injector nozzle of the first said cylinder isconveniently opened when the gas pressure therein has commenced or isincreasing in magnitude. Preferably, the delivery injector nozzle of thefirst said cylinder is opened while said piston supported therein hasinitiated or is undergoing a compression stroke.

Preferably, the delivery injector nozzle of the second said cylinder isopened at a point where the gas pressure in said cylinder is lower thanthe gas pressure in the gas supply system. Conveniently, the deliveryinjector nozzle of the second said cylinder is opened shortly before oronce said piston supported therein has reached the bottom dead centre(BDC) position of its travel. That is, the delivery injector nozzle ofthe second said cylinder is conveniently opened when the gas pressuretherein is at or near its lowest point. In this way, it is ensured thatsome or all of the gas that has been transferred into the gas supplysystem from the first said cylinder will subsequently be transferredfrom the gas supply system into the second said cylinder when thedelivery injector nozzle therefore is opened at the same time. Hence,injection may typically occur early in the cylinder cycle of the secondsaid cylinder such that it does not take place against a rising cylinderpressure.

Conveniently, the nozzle of the second said cylinder is opened when saidpiston supported therein is about to or has just completed an expansionor power stroke. With particular regard to a four-stroke cycle engine,the injector nozzle of the second said cylinder may also oralternatively be opened when said piston supported therein is about toor has just completed an intake or induction stroke. As far as normalengine running, the opening duration of the delivery injector nozzle ofthe second said cylinder is only a time related dependency. However, thestart of the fuel delivery event into the second said cylinder maypreferably be phased to crank angle so as to provide for a maximumdifferential gas pressure across the delivery injector nozzle of thesecond said cylinder. In this regard, in order to achieve such a maximumdifferential pressure, the timing of opening of the delivery injectornozzle of the second said cylinder is selected such that the associatedgas capture/transfer event on the first said cylinder has been at leastsubstantially or fully completed (ie: ensuring the maximum possible gaspressure has been transferred into the gas supply system). However, thetiming of opening of the delivery injector nozzle of the second saidcylinder cycle such that the pressure within the second said cylinderhas not substantially increased.

Accordingly, the fuel delivery event for the second said cylinder ispreferably a duration controlled event that commenced at a defined crankangle. Typical timings of the start angle for the fuel delivery event ona 3 cylinder 2-stroke engine may be between 110-120° BTDC whilst on a 4cylinder 4-stroke engine may be between 170-180° BTDC. A typicalduration for the opening period of the delivery injector nozzle of thesecond said cylinder for either engine configuration may be 6 ms.

As noted above, the method of operating an internal combustion engineaccording to the present invention may be effected during a start-upperiod of the engine. That is, the method may be effected until the mainsource of compressed gas is able to adequately pressurize the gas supplysystem for satisfactory fuel delivery to the engine. Alternatively, themethod of the present invention may be effected in combination with oneor more of the Applicants' prior known methods during the start-upperiod or even after that period.

For example, as alluded to hereinbefore, the opening time and/or periodof the injector nozzle of the first said cylinder may be such as toenable gas transfer to effect fuel delivery into the second saidcylinder (ie: without the need to bring the pressure in the gas supplysystem up to a predetermined level over a number of cylinder cycles) aswell as to provide some pressurisation of the gas supply system orvolume (ie: to a higher level). The opening and closing times of theinjector nozzle of the first said cylinder over successive openingsthereof may also be arranged to progressively increase the gas pressurein the gas supply system as well as to continue to effect gas transferto enable fuel delivery into the second said cylinder. That is, for anoptimized rate of rise of the pressure in the gas supply system, thecrank angle timing for successive gas capture/transfer events may besequenced such that crank angle opening and closing timings get closerto the TDC position of the first said cylinder as the pressure withinthe gas supply system rises. This will avoid any back flow of pressurefrom the gas supply system into the first said cylinder.

Further, pump-up events may continue to occur even after combustion istaking place in a cylinder in the manner as discussed in the Applicant'sPCT Patent Application No. PCT/AU97/00438, the contents of which areincluded herein by reference.

Conveniently, the gas supply system supplies gas to the deliveryinjector to effect the delivery of an air/fuel mixture to the engine.

In the case of engines having more than two cylinders, the method may beconducted sequentially over respective pairs of cylinders. It shouldhowever be noted that this method does not necessarily limit the methodsuch that successive cylinder pairs must be used in the method. It ispossible that one cylinder pair may be bypassed in the sequential eventsuch that there is no gas transfer between that cylinder pair.

Preferably, the opening of the delivery injector nozzles of the firstsaid cylinder and the second said cylinder may be overlapped over apredetermined period. In this way, gas which is transferred into the gassupply system from the first said cylinder effectively results in gasbeing immediately supplied to the second said cylinder through thedelivery injector nozzle thereof to thereby effect the delivery of fuelthereto.

In such a scenario, the delivery injector nozzle of the second saidcylinder may conveniently be opened at a point where the gas pressure insaid cylinder is lower than the gas pressure in the first said cylinder.It has been found that by overlapping the opening of the injectornozzles of the two noted cylinders, that the volume and pressure of thetransferred or displaced gas is sufficient to enable the satisfactorydelivery of fuel from the injector nozzle of the second cylinder.

It is to be noted that a metered quantity of fuel will typically bewholly or partly delivered to the delivery injector nozzle of the secondsaid cylinder prior to the transferred gas passing therethrough.Further, in certain circumstances, the metered quantity of fuel will bedelivered to the delivery injector nozzle once the transferred ordisplaced gas has commenced being delivered thereby.

Unlike previous systems, there is no requirement to pressurize the gassupply system over a number of cylinder cycles to a predetermined levelbefore fuel delivery is effected. Accordingly, this results in asignificantly shorter start-up period for the engine.

Preferably, the period of opening of the two injector nozzles may be atleast substantially identical.. For example, in regard to a threecylinder two-stroke engine, the injector nozzle of the first cylindermay be opened about the TDC point, for example between 90 degrees beforeTDC to 10 degrees after TDC, while the injector nozzle of the secondcylinder may be opened about the BDC point, for example between 210degrees before TDC to 110 degrees before TDC. The opening and closingtimes for the injector nozzles may be scheduled in the crank angledomain, time domain, or both, in accordance with known practice.

It is preferable that the delivery of the metered quantity of fuel,particularly during the start-up period, occurs before any significantpressure rise in the second said cylinder and so the inlet and/orexhaust ports of the second cylinder may be open at least during theinitial portion of the period of opening of the injector nozzle thereof.That is, the inlet and/or exhaust ports of the second cylinder may beopen for the duration or at least part of the fuel injection eventwithin the second cylinder. This ensures that the pressure within thesecond cylinder remains relatively low during the gastransfer/displacement event to thereby facilitate the injection of theair and fuel mixture into the cylinder.

The gas supply system may include a gas supply volume, typically an airrail, a compressor for supplying compressed gas to the gas supply volumeand a communication means between the gas supply volume and thecompressor. The gas supply volume may include an isolating means, forexample a one-way valve, as is described in the Applicant's PCT PatentApplication No. PCT/AU97/00438, the contents of which are incorporatedherein by reference. In this way, the gas supply volume may be isolatedfrom the compressor and preferably also the communication means, atleast during the start-up period of the engine. This ensures that gasdelivered from a first said injector nozzle is transferred into the gassupply volume and that gas is subsequently delivered therefrom to thenext injector nozzle without any of the gas within the gas supply volumeentering the volume provided by the communication means and by thecompressor. That is, the overall volume of the gas supply system duringstart-up is reduced which hence increases the gas flow rate from the gassupply system to the injector nozzle of the second cylinder.

According to another aspect of the present invention, there is providedan internal combustion engine having a plurality of cylinders eachrespectively supporting a piston therein, a fuel injection systemincluding a plurality of selectively operable delivery injector nozzles,and a gas supply system for supplying gas to the delivery injectornozzles, each delivery injector nozzle arranged to respectively deliverfuel by way of said gas directly into a said engine cylinder, saidengine including control means for controlling the engine so as to openthe delivery injector nozzles of a first said cylinder and of a secondsaid cylinder such that gas within the first said cylinder istransferred through the delivery injector nozzle thereof and into thegas supply system resulting in gas being supplied to the deliveryinjector nozzle of the second said cylinder to thereby effect thedelivery of fuel by way of the gas to the second said cylinder, whereineach second said cylinder into which fuel is delivered is operated toeffect combustion of said delivered fuel for each cylinder cycle.

Preferably the control means for controlling the engine does so byselecting the timing of opening and the open period of the first saidcylinder so as to provide for a maximum possible pressure to captured ortransferred into the gas supply system from the first said cylinder.Conveniently, some of this pressure will be retained in the gas supplysystem after the fuel has been delivered to the second said cylindersuch that the pressure in the gas supply system may eventually beincreased to a pre-determined level.

Preferably, the control means controls the timing of opening and theopen period of the delivery injector nozzle of the second said cylinderso as to provide for a maximum possible differential pressure betweenthe pressure within the gas supply system and the pressure within thesecond said cylinder.

Preferably, the control means controls the delivery injector nozzle ofthe first said cylinder such that it opens whilst said piston supportedtherein has initiated or is undergoing a compression stroke. Preferably,the control means controls the delivery injector nozzle of the secondsaid cylinder such that it opens at a point where the gas pressure insaid cylinder is lower than the gas pressure in the gas supply system.In particular, the control means may open the delivery injector nozzleof the first cylinder about the TDC point, while the control means mayopen the delivery injector nozzle of the second cylinder about the BDCpoint. Preferably, the control means for controlling the engine does soby overlapping the opening of the delivery injector nozzle of the firstsaid cylinder and the opening of the delivery injector nozzle of thesecond said cylinder.

Preferably, the control means controls the engine during a start-upperiod thereof.

The gas supply system may include a gas supply volume, typically an airrail, a compressor for supplying compressed gas to the gas supply volumeand a communication means between the gas supply volume and thecompressor.

An isolating means may be provided between the gas supply volume and thecompressor for isolating the compressor and preferably also thecommunication means from the gas supply volume, at least during thestart-up period of the engine. The provision of such an isolating meanshence allows for rapid pressurisation of the gas supply volume therebyreducing the start-up period of the engine when one of the earlier notedstart-up methods is used. The isolating means may include a one-wayvalve means located between the gas supply volume and the compressor.The communication means between the gas supply volume and the compressormay include a supply conduit and the valve means may alternatively belocated between the supply conduit and the gas supply volume. It is alsoenvisaged that the valve means may be located anywhere along the supplyconduit.

The invention will be more readily understood from the followingdescription of one preferred embodiment of a two fluid fuel injectionsystem for an internal combustion engine as illustrated in the drawings.

In the drawings;

FIG. 1 is a schematic view of a two fluid fuel injection system mountedon the cylinder head of an internal combustion engine illustrating themethod according to the present invention;

FIG. 2 is an injector timing chart for a three cylinder, two strokeengine operating according to the method of the present invention; and

FIG. 3 is an injector timing chart for the same engine as shown in FIG.2 depicting a different mode of operation according to the method of thepresent invention.

The present invention will be described with respect to a three cylindertwo stroke engine. It is however to be appreciated that the presentinvention is equally applicable to both two stroke and four strokeengines having two or more cylinders.

Referring initially to FIG. 1, there is shown a cylinder head 1 of a twostroke engine upon which is supported a two fluid fuel injection system2. The cylinder head 1 is shown in association with three cylinders 3,4, 5 provided within an engine block 20. Each cylinder supports a piston6 therein.

The two fluid fuel injection system 2 includes an air rail 7, and an airinjector 8 for each cylinder 3, 4, 5. Each air injector 8 is operativelyarranged in conjunction with a corresponding fuel injector 9, only oneof which is shown in FIG. 1 for clarity reasons. The air rail 7 suppliescompressed air to each of the air injectors 8 during normal operation ofthe engine, the air rail 7 typically being pressurized at around 650 kPasuch that the fuel delivered by the fuel injector 9 to the associatedair injector 8 can be effectively entrained and atomised when deliveredto the associated cylinder 3, 4, 5. The air rail 7 is typically arrangedto receive compressed air from an air compressor.

It is to be noted that whilst the present embodiment relates to a dualfluid injection system where a separate fuel injector 9 is provided inassociation with each deliver injector 8, the present invention isequally applicable to other dual fluid fuel injection systems wherein,for example, the fuel to be delivered by the compressed gas is meteredby one or more positive displacement means or some other passive fuelmetering means. Further, the present invention is equally applicable todual fluid injection systems which rely on means other than a compressorto provide the compressed gas for fuel delivery during normal operation.For example, the present invention is equally applicable to systemswhich rely on cylinder pressure entrapment such as that described in theApplicant's U.S. Pat. No. 5,622,155, the contents of which areincorporated herein by reference.

The time involved in bringing the air rail 7 up to the desired normaloperational pressure can be quite significant, for example, at least onesecond. This may restrict the use of such dual fluid fuel injectionsystems in certain applications such as in cord or pull start engineswhere there is very little time to fire up the engine. The methodaccording to the present invention therefore seeks to provide asignificant reduction of the start-up time.

According to the present invention, during engine start-up, the deliveryinjector nozzle 10 of the air injector 8 of a first cylinder 5 may beopened during a compression stroke of the piston 6 of the cylinder 5 asthe piston 6 approaches it's TDC position. Furthermore, the deliveryinjector nozzle 10 of the air injector 8 of a second cylinder 3 may beopened during an expansion or intake stroke of the piston 6 of thatcylinder 3 as the piston 6 is near or immediately after it's BDCposition. An overlap of the opening of the delivery injector nozzle 10of the first or “delivery” cylinder 5 and the second or “receiving”cylinder 3 is provided such that there is a gas transfer or displacementfrom the delivery cylinder 5 through its delivery injector nozzle 10into the air rail 7 and from the air rail 7 into the receiving cylinder3 through its delivery injector nozzle 10. This gastransfer/displacement process enables the delivery of an air/fuel chargeto the receiving cylinder 3. That is, gas flow into the air rail 7effectively increases the gas pressure therein whereupon some gas exitsthe air rail 7 into the receiving cylinder 3. FIG. 1 shows schematicallythe gas transfer process with the gas 11 from the delivery cylinder 5flowing through the injector nozzle 10 thereof, and resulting in gasflow through the air rail 7 in the general direction as shown by theflow line 12 leading from the delivery injector nozzle 10 of thedelivery cylinder 5 to the delivery injector nozzle 10 of the receivingcylinder 3. This gas transfer/displacement process then effects thedelivery of a metered quantity of fuel 13 into the receiving cylinder 3.The gas is therefore effectively transferred directly between thecylinders and there is effectively little to no “pump-up” of the airrail 7. Following this effective gas transfer, the method can beconducted sequentially over other respective pairs of cylinders of theengine as shown in FIG. 2. It has been found that this arrangement canprovide 70 to 90 kPa of pressure to the delivery injector nozzle 10 ofthe receiving cylinder 5. It is however to be noted that, as alluded tohereinbefore, the method of the present invention may be implementedsuch that some pressurisation of the air rail 7 does take place whilstgas from one cylinder is being used to affect fuel delivery into asecond cylinder. In this way, the pressure within the air rail 7 may beprogressively increased to a predetermined level whilst fuel is beingdelivered to the engine cylinders by way of the gastransfer/displacement method as described according to the presentinvention.

During normal operation of the engine, an air compressor providescompressed air to the air rail 7. A one-way valve can be providedbetween the compressor and the air rail 7 to isolate the compressor fromthe air rail 7 during the start-up sequence described above. The one-wayvalve will however remain permanently open when the compressor beginsdelivering compressed air at the normal operating pressure.

FIG. 2 shows the injector timing chart for a three cylinder two strokeengine when the method of the present invention is employed. This chartshows the typical injector timings during the start-up of such anengine. The period of opening of the delivery nozzles 10 of the threecylinders are shown as periods A1, A2 and A3 respectively, whereas theperiod of opening of the fuel injectors of the three cylinders are shownas periods F1, F2 and F3 respectively in the chart. The TDC positionsfor each cylinder are shown spaced apart 120° about the chart.

Referring initially to the TDC position of the first cylinder (TDC1)shown at the top of the chart, the delivery injector nozzle 10 of thefirst cylinder 3 is opened prior to TDC1 over the period A1. The firstcylinder 3 is therefore undergoing a compression stroke prior to TDC1.At the same time, the delivery nozzle 10 of the second cylinder 4 isopened over the period A2 with the second cylinder 4 completing anexpansion stroke and commencing a compression stroke as it passesthrough it's BDC position. The fuel injector 9 of the second cylinderalso supplies fuel to the delivery injector nozzle 10 of the secondcylinder 4 over period F2. All these periods A1, A2, F2 overlapresulting in the delivery of atomised fuel to the second cylinder 4. Thechart shows the delivery injector nozzles 10 of the first and secondcylinders 3, 4 opening simultaneously for the same period. It is howeverto be appreciated that the delivery injector nozzles 10 of these or anyother pairs of cylinders do not need to open at the same time or providean overlap of the opening of the delivery injector nozzles thereof.

The TDC position of the second cylinder (TDC2) is shown in the 120°position of the chart. Immediately prior to the TDC2 position as thesecond cylinder 4 is undergoing a compression stroke, both the deliveryinjector nozzle of the second and third cylinders 4 and 5 are openedover periods A2 and A3 respectively. As the fuel injector 9 of the thirdcylinder 5 is supplying fuel to the injector nozzle of the thirdcylinder 5 over period F3, the air transferred from the second cylinder4 enables the delivery of fuel to the third cylinder 5.

The TDC position of the third cylinder (TDC3) is shown in the 240°position of the chart. The injector nozzles 10 of the third and firstcylinders 5, 3 are both opened over periods A3 and A1 respectively, andthe fuel injector 9 of the first cylinder 3 is opened over period F1 toeffect delivery of fuel into the first cylinder 3 in the same manner asdescribed above.

Because the fuel is injected into a receiving cylinder before there isany substantial pressure rise therein, this allows for the transfer ordisplacement of gas between the cylinders to occur, the deliverycylinder typically being at a higher pressure than the receivingcylinder. Therefore, the delivery cylinder is typically undergoing acompression stroke while the receiving cylinder is typically undergoingan expansion stroke. The receiving cylinder typically receives air aboutor just after the BDC position thereof.

FIG. 3 shows the injector timing chart for a three cylinder two strokeengine wherein a variation of the method of the present invention isemployed. The period of opening of the delivery injector nozzles 10 areagain shown as periods F1, F2 and F3. As per FIG. 2, the chart shows thetypical injector timings during start-up of the engine with the TDCpositions for each cylinder being shown spaced apart 120° about thechart.

Assuming that the engine start-up routine is commenced just after TDC3,it will be seen that the delivery injector nozzle 10 of the firstcylinder 3 is opened prior to TDC1 over the period A1. In this instance,the delivery injector nozzle of the first cylinder 3 may also be heldopen for a short period after TDC1. The pressure within the firstcylinder 3 is generally increasing during the period A1 and hence thisfirst opening of the delivery injector nozzle 10 of the first cylinder 3serves to transfer/capture a maximum possible pressure in the air rail7. Some time after the commencement of the period A1, the fuel injector9 of the second cylinder 4 is opened to commence metering a quantity offuel to the delivery injector nozzle 10 of the second cylinder 4. Inthis instance, this fuel metering event is completed prior to theopening of the fuel metering nozzle 10 of the second cylinder 4.

As can be seen from the timing chart, the timing of opening of thedelivery injector nozzle 10 of the second cylinder 4 is opened whilstthe delivery injector nozzle 10 of the first cylinder 3 is still open.This is done to enable the maximum possible pressure to be transferredinto the air rail 7, but also such that the delivery of fuel may occurinto the second cylinder 4 when the pressure rise therein. In thisconnection it will be noted that the transfer and exhaust parts of thesecond cylinder 4 of the two stroke engine will still be opened duringpart or all of the period A2 and will hence contribute to their being adesirable pressure differential across the delivery injector nozzle 10of the second cylinder 4.

Hence, the pressure which is captured/transferred into the air rail 7during the period A1 is used to effect fuel delivery into the secondcylinder 4 over the period A2. As alluded to hereinbefore, a portion ofthe pressure delivered into the air rail 7 during the period A1 may beretained in the air rail 7 subsequent to the period A2. In this way, thepressure within the air rail 7 may be progressively increased to raiseit up to a predetermined level whilst fuel is being delivered by way ofcaptured/transferred gas into the cylinders of the engine.

The TDC position of the second cylinder 4 (TDC2) is again shown at the120° position of the chart. As can be seen, the routine as describedabove is repeated wherein gas pressure is delivered into the air rail 7over the period A2 and subsequently used to deliver fuel (which has beendelivered to the delivery injector nozzle 10 of the third cylinder 5over the period F3) into the third cylinder 5 over the period A3. In asimilar manner, gas is transferred into the air rail 7 from the secondcylinder 4 whilst the pressure therein is increasing (mainly on thecompression stroke) and a portion of the gas pressure is then used toeffect fuel delivery into the third cylinder 5 at a time when there is amaximum differential pressure existing between the pressure in the thirdcylinder 5 (wherein the piston 6 has only recently commenced itscompression stroke).

The TDC position of the third cylinder 5 (TDC3) is shown in the 240°position of the chart. The injector nozzles 10 of the third and firstcylinders 5, 3 are both opened over periods A3 and A1 respectively, andthe fuel injector 9 of the first cylinder 3 is opened over the period F1to affect delivery of fuel into the first cylinder 3 in the same manneras described above.

By way of this variation to the method of the present invention, it isevident that whilst there is some overlaps between the open periods ofthe injector nozzles 10 of a delivering cylinder and a receivingcylinder, these open periods are different in duration and timing. Ascan be seen from the chart, the typical open period for the deliveryinjector nozzle 10 of a cylinder when being used to transfer gaspressure into the air rail 7 is for example between 90° BTDC and 10°ATDC. The typical timing of opening for the delivery injector nozzle 10of a cylinder when being used to deliver fuel into a receiving cylinderis for example between 120° to 110° BTDC.

It is also envisaged that the method according to the present inventionmay be combined with the method described in the Applicant's earlierU.S. Pat. No. 4,936,279 or the method discussed in the Applicant's PCTPatent Application No. PCT/AU97/00438 such that by adjusting the timingsof the opening of the delivery injector nozzles 10 as shown in PCTPatent Application No. PCT/AU97/00438, a degree of pump-up of the airrail 7 can still occur.

An important point to note in regard to the method of the presentinvention is that the delivery injector nozzle 10 of a cylinder istypically required to open twice during a single cylinder cycle. A firstopening of the delivery injector nozzle 10 during the cylinder cycle isused to perform a fuel delivery event to the cylinder. A second openingof the same delivery injector nozzle 10 is used to perform or gascapture/transfer event such that the gas pressure provided by thecylinder may be used to effect the delivery of fuel by way of gas into adifferent cylinder. Hence, both functions are performed by the onedelivery injector nozzle 10 as is evidenced in FIGS. 2 and 3.

It has been found that the method according to the present invention canreduce the start-up time for the engine to around 0.6 to 0.7 seconds. Itshould be noted that the minimal delay in engine start-up according tothe present invention is still required because the encoder of theengine must typically determine the angular position of the enginebefore the method according to the present invention may operate. Thiscan take up to ⅓ or 1 ⅓ revolutions of the crankshaft of the engine fromthe beginning of engine start sequence.

It is possible that, during the start-up of the engine, some fuel mayalso be transferred between cylinders. This is due to the fact that, inusing the method according to the present invention, a receivingcylinder may in turn become a delivery cylinder after it has had fueldelivered thereinto by way of gas from the air rail 7 being transferredthrough the delivery injector nozzle 10 thereof. Hence, when thedelivery injector nozzle 10 of this cylinder is subsequently opened (ormaintained open following the initial delivery of fuel thereby) toenable some gas to be transferred into the air rail 7 during thecompression stroke of the piston 6 supported therein, some fuel(previously delivered into this cylinder) may also be transferred intothe air rail 7. However, it has been found that this does not adverselyeffect the operation of the engine at start-up.

The present invention is also applicable to other multi-cylinder engineconfigurations such as V-engines. For example, in a V 6 engine, the twoseparate banks of cylinders may be made to operate independently duringa start-up period wherein the method according to the present inventionis used separately in relation to each bank of cylinders. Once theengine has successfully completed start-up, it may then be operated inthe normal manner.

The above description is provided for the purposes of exemplificationonly and it will be understood by a person skilled in the art thatmodifications and variations may be made without departing from theinvention.

What is claimed is:
 1. A method of operating an internal combustionengine, the engine having a plurality of cylinders each respectivelysupporting a piston therein, a fuel injection system including aplurality of selectively operable delivery injector nozzles, and a gassupply system for supplying gas to the delivery injector nozzles, eachdelivery injector nozzle arranged to respectively deliver fuel by way ofsaid gas directly into a said engine cylinder, the method includingopening the delivery injector nozzles of a first said cylinder and asecond said cylinder such that gas within the first said cylinder istransferred through the delivery injector nozzle thereof and into thegas supply system resulting in the gas being supplied to the deliveryinjector nozzle of the second said cylinder to thereby effect thedelivery of fuel thereto, wherein each of the first and second saidcylinders are operated to effect combustion during a respective cylindercycle in a same engine cycle, and wherein the delivery injector nozzlesof the first and second cylinders are simultaneously open for a periodin said same engine cycle when the transfer of gas from the first saidcylinder into the gas supply system results in gas and fuel beingsupplied to the second said cylinder.
 2. A method according to claim 1,wherein the timing of opening and the open period of the deliveryinjector nozzle of the first said cylinder are selected to enable themaximum possible pressure to be transferred into the gas supply systemfrom the first said cylinder.
 3. A method according to claim 1, whereinthe timing of opening of the delivery injector nozzle of the second saidcylinder is selected to provide the maximum possible pressuredifferential across the delivery injector nozzle.
 4. A method accordingto claim 1, wherein a portion of the gas transferred through thedelivery injector nozzle of the first said cylinder is retained in thegas supply system subsequent to the delivery of fuel by way of the gasto the second said cylinder.
 5. A method according to claim 1, whereinthe opening and closing of the delivery injector nozzle of the firstsaid cylinder is controlled with respect to crank angle.
 6. A methodaccording to claim 1, wherein the delivery injector nozzle of the firstsaid cylinder is opened when the gas pressure therein has commenced oris increasing in magnitude.
 7. A method according to claim 1, whereinthe delivery injector nozzle of first said cylinder is opened while saidpiston supported therein has initiated or is undergoing a compressionstroke.
 8. A method according to claim 1, wherein the delivery injectornozzle of the second said cylinder is opened at a point where the gaspressure in the second said cylinder is lower than the gas pressure inthe gas supply system.
 9. A method according to claim 1, wherein thedelivery injector nozzle of the second said cylinder is opened shortlybefore or once travel of said piston supported therein has reached thebottom dead centre (BDC).
 10. A method according to claim 1, wherein thedelivery injector nozzle of the second said cylinder is opened when saidpiston supported therein is about to or has just completed an expansionor power stroke.
 11. A method according to claim 1, wherein the deliveryinjector nozzle of the second said cylinder is controlled as a durationbased event that commences at a defined crank angle.
 12. A methodaccording to claim 1, wherein the opening of the delivery injectornozzles of the first said cylinder and the second said cylinder areoverlapped over a predetermined period.
 13. A method according to claim1, wherein in engines having more than two cylinders, the method isconducted sequentially over respective pairs of cylinders.
 14. A methodaccording to claim 1, wherein the period of opening of the two deliveryinjector nozzles is at least identical.
 15. A method according to claim1, wherein the engine is a four-stroke engine, and wherein the deliveryinjector nozzle of the second said cylinder is opened when said pistonsupported therein is either about to complete an intake stroke or hasjust completed an intake of stroke.
 16. A method according to claim 1,including modifying the timing of the opening and closing of thedelivery injector nozzle of the first said cylinder to provide aprogressive increase of the pressure within the gas supply system.
 17. Amethod according to claim 1, the engine being a three cylindertwo-stroke engine, the delivery injector nozzle of the first saidcylinder being opened about the TDC point, while the delivery injectornozzle of the second said cylinder is opened about the BDC point.
 18. Amethod according to claim 17, the engine being a three cylinder engine,wherein the delivery injector nozzle of the first said cylinder isopened between 90 degrees before TDC to 10 degrees after TDC, and thedelivery injector nozzle of the second said cylinder is opened between210 degrees before TDC to 110 degrees before TDC.
 19. A method accordingto claim 1, wherein the fuel is wholly or partly delivered to thedelivery injector nozzle of the second said cylinder prior to theopening of the delivery injector nozzle thereof.
 20. A method accordingto claim 1, wherein the fuel is delivered to the delivery injectornozzle of the second said cylinder subsequent to the opening of thedelivery injector nozzle thereof.
 21. A method according to claim 1,wherein the delivery of fuel to the second said cylinder occurs beforeany significant pressure rise in the second said cylinder.
 22. A methodaccording to claim 21, wherein inlet and/or exhaust ports of the secondsaid cylinder are opened at least during the initial portion of theperiod opening of the delivery injector nozzle thereof.
 23. A methodaccording to claim 1, wherein the delivery injector nozzle of a cylinderis opened twice during a single cylinder cycle.
 24. A method accordingto claim 1, wherein the method is used during start-up of the engine.25. A method according to claim 1, wherein a cylinder which initiallydelivers gas into the gas supply system to enable the delivery of fuelto another cylinder subsequently receives gas from the gas supply systemto enable the delivery of fuel thereinto.
 26. A method according toclaim 1, wherein the delivery injector nozzle of a cylinder is operatedto permit both the transfer of gas to and from the cylinder within asingle cylinder cycle.
 27. A method according to claim 1, wherein fuelis entrained in said gas prior to passing through the delivery injectornozzle of the second said cylinder.
 28. A method according to claim 1,wherein the fuel is delivered to the second said cylinder during aninitial rotation of the engine.
 29. An internal combustion engine havinga plurality of cylinders each respectively supporting a piston therein,a fuel injection system including a plurality of selectively operabledelivery injector nozzles, and a gas supply system for supplying gas tothe delivery injector nozzles, each delivery injector nozzle arranged torespectively deliver fuel by way of said gas directly into a said enginecylinder, said engine including control means for controlling the engineso as to open the delivery injector nozzles of a first said cylinder andof a second said cylinder such that gas within the first said cylinderis transferred through the delivery injector nozzle thereof and into thegas supply system resulting in the gas being supplied to the deliveryinjector nozzle of the second said cylinder to thereby effect thedelivery of fuel thereto, wherein each of the first and second saidcylinders are operated to effect combustion during a respective cylindercycle in a same engine cycle, and wherein the delivery injector nozzlesof the first and second said cylinders are simultaneously open for aperiod in said same engine cycle when the transfer of gas from the firstsaid cylinder into the gas supply system results in gas and fuel beingsupplied to the second said cylinder.
 30. An engine according to claim29, wherein the timing of opening and the open period of the deliveryinjector nozzle of the first said cylinder are selected to enable themaximum possible pressure to be transferred into the gas supply systemfrom the first said cylinder.
 31. An engine according to claim 29,wherein the timing of opening of the delivery injector nozzle of thesecond said cylinder is selected to provide the maximum possiblepressure differential across the delivery injector nozzle.
 32. An engineaccording to claim 29, wherein a portion of the gas transferred throughthe delivery injector nozzle of the first said cylinder is retained inthe gas supply system subsequent to the delivery of fuel by way of thegas to the second said cylinder.
 33. An engine according to claim 29,wherein the control means controls the delivery injector nozzle of thefirst said cylinder such that it opens whilst said piston supportedtherein has initiated or is undergoing a compression stroke.
 34. Anengine according to claim 29, wherein the control means controls thedelivery injector nozzle of the second said cylinder such that thedelivery injector nozzle of the second said cylinder opens at a pointwhere the gas pressure in the second said cylinder is lower than the gaspressure in the gas supply system.
 35. An engine according to claim 29,wherein the control means opens the delivery injector nozzle of thefirst said cylinder about the TDC point, while the control means opensthe delivery injector nozzle of the second said cylinder about the BDCpoint.
 36. An engine according to claim 29, wherein the control meansfor controlling the engine controls the engine by overlapping theopening of the delivery injector nozzle of the first said cylinder andthe opening of the delivery injector nozzle of the second said cylinder.37. An engine according to claim 29, wherein the delivery injectornozzle of a cylinder is opened twice during a single cylinder cycle. 38.An engine according to claim 29, wherein the control means controls theengine during a start-up period thereof.
 39. An engine according toclaim 29, wherein the gas supply system includes a supply of gas, acompressor for supplying compressed gas to the supply of gas and acommunication means between the supply of gas and the compressor.
 40. Anengine according to claim 39, wherein an isolating means is providedbetween the gas supply volume and the compressor for isolating thecompressor.
 41. An engine according to claim 40, wherein the isolatingmeans further isolates the communication means from the gas supplyvolume, at least during the start-up period of the engine.
 42. An engineaccording to claim 40, wherein the isolating means includes a one-wayvalve means located between the gas supply volume and the compressor.43. An engine according to claim 42, wherein the communication meansbetween the gas supply volume and the compressor includes a supplyconduit and the valve means is located between the supply conduit andthe gas supply volume.
 44. An engine according to claim 29, wherein thesupply of gas from the first said cylinder into the gas supply systemand the supply of gas to the second said cylinder from the gas supplysystem occur during the same cylinder cycle.
 45. An engine according toclaim 29, wherein a cylinder which initially delivers gas into the gassupply system to enable the delivery of a fuel to another cylindersubsequently receives gas from the gas supply system to enable thedelivery of fuel thereinto.
 46. An engine according to claim 29, whereinfuel is entrained in said gas prior to passing through the deliveryinjector nozzle of the second said cylinder.
 47. An engine according toclaim 29, wherein the fuel is delivered to the second said cylinderduring an initial rotation of the engine.
 48. A method of operating aninternal combustion engine, the engine having a plurality of cylinderseach respectively supporting a piston therein, a fuel injection systemincluding a plurality of selectively operable delivery injector nozzles,and a gas supply system for supplying gas to the delivery injectornozzles, each delivery injector nozzle arranged to respectively deliverfuel by way of said gas directly into a said engine cylinder, the methodincluding opening the delivery injector nozzles of a first said cylinderand a second said cylinder such that gas within the first said cylinderis transferred through the delivery injector nozzle thereof and into thegas supply system resulting in the gas being supplied to the deliveryinjector nozzle of the second said cylinder to thereby effect thedelivery of fuel thereto, wherein each of the first and second saidcylinders are operated to effect combustion during a respective cylindercycle in a same engine cycle, and wherein the open delivery injectornozzles of the first said cylinder and the second said cylinder overlapover a predetermined period in said same engine cycle and said gas issupplied to the delivery iniector nozzle of the second said cylinder todeliver fuel while the delivery injector nozzles of said first andsecond cylinders are simultaneously open.
 49. A method according toclaim 48, wherein the fuel is delivered to the second said cylinderduring an initial rotation of the engine.
 50. An internal combustionengine having a plurality of cylinders each respectively supporting apiston therein, a fuel injection system including a plurality ofselectively operable delivery injector nozzles, and a gas supply systemfor supplying gas to the delivery injector nozzles, each deliveryinjector nozzle arranged to respectively deliver fuel by way of said gasdirectly into a said engine cylinder, said engine including controlmeans for controlling the engine so as to open the delivery injectornozzles of a first said cylinder and of a second said cylinder such thatgas within the first said cylinder is transferred through the deliveryinjector nozzle thereof and into the gas supply system resulting in thegas being supplied to the delivery injector nozzle of the second saidcylinder to thereby effect the delivery of fuel thereto, wherein each ofthe first and second said cylinders are operated by said control meansto effect combustion during a respective cylinder cycle in a same enginecycle, and wherein the control means for controlling the engine does soby overlapping the opening of the delivery injector nozzle of the firstsaid cylinder and the opening of the delivery injector nozzle of thesecond said cylinder in said same engine cycle and said gas is suppliedto the delivery iniector nozzle of the second said cylinder to deliverfuel while the delivery iniector nozzles of said first and secondcylinders are simultaneously open.
 51. An engine according to claim 50,wherein the fuel is delivered to the second said cylinder during aninitial rotation of the engine.